The use of air filters in Heating-Ventilating-Air-Conditioning (HVAC) systems have at least two beneficial purposes. For one, they improve the efficiency of the HVAC system by removing airborne contaminants from the air that that would otherwise flow with the air through components of the HVAC system. Specifically, as is well known, airborne contaminants are a major contributor for adversely affecting the operational efficacy of an HVAC system. The other purpose for using an air filter in an HVAC system is to improve the air quality in the environment that is being serviced by the system.
It is well known that over time, air filters become dirty and less efficient. Thus, in order to maintain an acceptable level of filter efficacy it is expected, and is indeed necessary, to periodically replace air filters. It is also known that the efficiency of an air filter can be improved, and their replacement times extended, by increasing the air filter surface that is exposed to the column of air which is being filtered. One way to do this is by orienting the air filter with its exposed surface at an angle to the direction of air flow.
In light of the above, it is an object of the present invention to provide an air filter for use in a Heating-Ventilating-Air-Conditioning (HVAC) system that establishes a tortuous path for a filter medium, to thereby increase the surface area of the filter medium across the airflow channel for filtering air as the air moves through the airflow channel. Another object of the present invention is to provide an air filter for use in a Heating-Ventilating-Air-Conditioning (HVAC) system which automatically replaces used filter medium with new, unused filter medium in accordance with a predetermined schedule, by periodically rotating a take-up roll to advance the filter medium from a supply roll to the take-up roll along the tortuous path. Still another object of the present invention is to provide an air filter system for use in a Heating-Ventilating-Air-Conditioning (HVAC) system which is easy to manufacture and install, is simple to operate, and is relatively cost effective.